The invention relates to a process for the regulation of the optimum operational behavior of an internal combustion engine by engagement of the fuel-air metering device, in dependence on fluctuations of engine operating parameters.
The purpose of the process is to achieve an optimum behavior of the internal combustion engine in the entire characteristic field of operation, for example, by a corresponding consumption of fuel, composition of the exhaust gas and engine smoothness.
As is well known, whenever a piston-type internal combustion engine is operated with a mixture of fuel and air which is leaner than the stoichiometric relation, the engine exhibits irregular combustion which leads to rough running. This rough or unstable running is due to the slight dispersions in the charging coefficient from cylinder to cylinder and in successive operational cycles of the same cylinder.
An engine control process based on the magnitude of the unstable engine behavior therefore requires a quantitative and reliable measurement of the pertinent fluctuations of engine variables.
Since the irregular combustion also causes uneven rotation of the crankshaft, it has already been proposed to utilize the dispersion (scattering) of the elapsed time between angular marks on the crankshaft for the measurement of the irregularity of the combustion and to deduce therefrom the correction of the fuel quantity to be injected. However, a major disadvantage of this process is that unavoidable vibrations of the vehicle, due to irregularities in the roadbed, as well as shocks transmitted by the driving wheels through the transmission, are also transferred to the crankshaft.
It has further been proposed to use the ion current in the combustion chamber as a measuring variable for the fluctuations of combustion, and these fluctuations are adjusted to the permissible theoretical value (set-point value) by correction of the fuel-air ratio. This method requires a measuring probe in each cylinder and, apart from the expense, it raises the problem of making identical measurements in the individual cylinders and also has disadvantages due to aging.